The structural proteins of small RNA viruses can play non-structural roles during replication. Besides forming the nucleocapsid, the N protein of porcine reproductive and respiratory syndrome virus (PRRSV) possesses two unique properties; nucleolar localization and the induction cell death. Both properties map to a highly conserved region, having no homology with known viral or cellular proteins. The specific aims of this project are to characterize the determinants of the N protein responsible for nuclear-nucleolar localization and cell death, and identify possible roles for the N protein in the modulation of host cell biosynthesis. The first objective is to determine the minimal amino acid sequence that comprises the N protein nucleolar localization signal (NoLS) and identify the importance of individual arginine, lysine and histidine residues. This is accomplished using enhanced green fluorescent protein (EGFP) as a tag. Objective 2 is directed at identifying the requirement of a nuclear localization signal (NLS) and energy to transport N across the nuclear membrane. The third objective is to evaluate RNA synthesis, protein synthesis and apoptosis in cells during PRRSV infection and after expression of the N protein. The fourth objective is the productive integration of undergraduate students into research.